This invention relates to a process for preparing alditol acetals, such as dibenzylidene sorbitols, monobenzylidene sorbitols, and the like, through the reaction of unsubstituted or substituted benzaldehydes with alditols (such as sorbitol, xylitol, and ribitol) in the presence of a mineral acid and at least one surfactant having at least one pendant group of 6 carbon chains in length. Such a reaction provides a cost-effective, relatively safe procedure that provides excellent high yields of alditol acetal products, particularly those which have heretofore not been readily available due to processing limitations, such products including bis(5-indanylidene)sorbitol. Furthermore, such a specific reaction is also the best known procedure for the production of certain compounds which can be easily separated from other formed isomers. Additionally, such a procedure facilitates the production of certain asymmetric alditol acetal compounds and compositions in acceptable yields as well. Such alditol acetals are useful as nucleating and clarifying agents for polyolefin formulations and articles, as one example.
All U.S. Patent documents and other publication discussed below are herein entirely incorporated by reference.
Dibenzylidene sorbitol (xe2x80x9cDBSxe2x80x9d), substituted DBS""s, such as can be made with alkyl substituted aromatic aldehydes, and related acetals have found utility as nucleating agents, clarifying agents, gelling agents, processing aids, and strength modifiers in polyolefin resins, polyester resins, deodorant, and antiperspirant compositions; hydrocarbon fuels; waste liquids, especially those containing organic impurities; and paint.
Alditol acetals, such as DBS derivative compounds, are typically prepared by the condensation reaction of an aromatic aldehyde with a polyhydric alcohol, for example, without limitation, sorbitol, xylitol, ribitol, and the like. For DBS structures, such reactions involve two moles of the aldehyde and one mole of the alcohol. Examples of suitable processes may be found in Uchiyama, U.S. Pat. No. 4,267,110, Murai et al., U.S. Pat. No. 3,721,682; Murai et al., U.S. Pat. No. 4,429,140; Machell, U.S. Pat. No. 4,562,265; Kobayashi et al., U.S. Pat. No. 4,902,807; Salome et al., U.S. Pat. No. 5,023,354; and Scrivens et al., U.S. Pat. No. 5,731,474.
Unfortunately, these previous reaction procedures all suffer significant drawbacks for utilization within a greater breadth of reactions. The first procedure taught was by Uchiyarna solely for the production of limited DBS compounds of the unsubstituted benzaldehyde type. The lack of versatility of such a procedure has severely limited its implementation within different DBS compound producing methods. Solvent-based systems have been developed for higher yield and greater versatility of DBS formation, for instance, within the Murai et al., Scrivens et al, and Kobayashi et al. patents, which all concerned reactions for the production of un-, mono-, or di-substituted dibenzylidene sorbitols. Although these reactions are highly effective in producing high yield, high purity DBS compounds, the solvents needed are expensive and the energy required to effectuate necessary mixing and high temperatures is also expensive. In an effort to reduce such solvent costs, low temperature low temperature aqueous procedures have been developed, such as in the Machell and Salome et al. patents. Machell requires the utilization of a mineral acid as the catalyst alone for acetalization; Salome et al. specifically exclude any mineral acids from their procedure and instead rely solely upon the presence of relatively large amounts of arylsulfonic acid catalysts to effectuate acetalization of the benzaldehyde and alditol components. Machell thus requires large amounts of mineral acids whereas Salome et al. require expensive arylsulfonic compounds (such as para-toluenesulfonic acid, naphththalene sulfonic acid, and the like). More importantly, however, it has now been found that there are key problems with both types of procedures which require improvement. For instance, the previous uses of acid alone, as in Machell, or with arylsulfonic acids alone, as in Salome et al., as acetalization catalysts have proven very difficult for a number of reasons. The Machell method of acid alone has suffered from a lack of effectiveness in producing highly-substituted DBS derivatives, apparently, and without intending to be limited to any specific scientific theory, from the lack of contacting a sufficient amount of catalyst with the reactants themselves to permit combination and thus acetalization. In the past, such mineral acids have proven to be excellent catalysts alone for un- or certain minimally-substituted benzaldehydes (e.g., p-methylbenzaldehyde). Apparently, di-substituted benzaldehydes and above are more hydrophobic and thus do not solubilize well within aqueous acid formulations. In such a situation, the catalysis of di-substituted (or higher)benzaldehydes with alditol is nearly nonexistent due to a lack of effective contact between all three components (e.g., acid, benzaldehyde, and alditol). Benzaldehyde and p-methylbenzaldehyde, on the other hand, are much more soluble within such an aqueous acid formulation and thus more easily contact the acid catalyst, thereby permitting a more effective acetalization of the alditol for very high yields. Thus, from a versatility standpoint, the use of mineral acids alone, although the best catalyst for acetalization procedures, does not effectively contact with certain reactants due to solubility considerations. The Salome et al. method requires a very large amount of very expensive arylsulfonic compounds (Salome et al. require a molar ratio of benzaldehyde to arylsulfonic acid of at least 1:0.6) as catalysts alone within the reaction mixture. Although such large amounts of arylsulfonic acid catalyst have proven to be effective for certain reactions of benzaldehydes with alditols, a combination of both costs and lack of versatility has been problematic from a large-scale industrial production standpoint. The arylsulfonic acids alone either do not contact sufficiently (as with p-toluenesulfonic acid) or are not strong enough acid catalysts alone to provide the needed reactivity for greater versatility with different benzaldehyde reactants at lower levels at concentration within the reaction mixture. Thus, the cost of such arylsulfonic acids, being relatively high and extremely high in comparison with the more effective mineral acids, pose considerable economic problems for the user.
Clearly, the utilization of less expensive mineral acids, which are better catalysts at lower amounts, is a preferred method from a cost perspective; however, the lack of versatility has been a hindrance to widespread use and effectiveness of such a method. The yield offered by both teachings is acceptable, however the versatility of producing large variations of different DBS compounds is questionable. There has been a need to provide a procedure which permits production of not only standard p-methyldibenzylidene sorbitol (MDBS), 3,4-dimethyldibenzylidene sorbitol (DMDBS), and dibenzylidene sorbitol (DBS), but other compounds which heretofore have been impossible to produce either at all or at least in any acceptable yield and/or purity. As a few examples, 1,3:2,4-bis(5-indanylidene)sorbitol has been unavailable as a product due to the lack of production of such a compound in any yield acceptable on an industrial scale or without the need for using excess amounts of the reactive benzaldehyde. Such a compound is known to provide excellent clarifying and nucleating benefits within polypropylene formulations, but, again, has not been readily utilized in such a market because of the lack of effective production methods for large-scale reliable availability. Also, other types of compounds, such as certain symmetrical compounds [e.g., 1,3:2,4-bis(3-ethyl-4-methylbenzylidene)sorbitol and 1,3:2,4-bis(3,4-diethylbenzylidene) sorbitol] have not been available as pure product due to the presence of isomers and/or reaction mixture additives which could not be readily removed or separated from the desired compounds. With the lack of versatility, cost problems, potential corrosiveness, or all three, the above-listed and discussed methods have proven ineffective in providing needed advances in DBS production technology. Without any further teachings or fair suggestions, expansions into other DBS compound areas to develop alternative and more specialized polyolefin nucleation and/or clarification markets and products has been hampered. Hence, there is a need to develop a procedure to facilitate high yield, reliable, versatile, cost-effective, and safe production of both standard and novel alditol acetal derivative compounds. To date, again, although some processes do exist permitting production of limited types of DBS compounds, or provide some versatility, but at a rather large cost economically, there simply is no effective alternative to expand the production capabilities of a wide array of such alditol acetal derivatives.
Therefore, an object of the invention is to provide a process a highly versatile process for producing high yields of alditol acetal derivative compounds, most notably, without limitation symmetrical and asymmetrical DBS compounds. A further object of the invention is to provide a highly effective manner of producing such compounds which heretofore could not be produced in high yields without incurring potential problems from cost and/or safety perspectives, particularly in a large-scale procedure. Another object of the invention is to provide a method which also permits the production of monoacetal derivatives and asymmetrical dibenzylidene compounds. Additionally, it is an object of this invention to provide a method of producing alditol acetal derivative compounds which permits the utilization of any type of surfactant component thereby facilitating utilization of such a procedure on a widespread basis and permitting the user greater versatility and fewer limitations on reaction component selections.
Accordingly, this invention encompasses a method of producing an alditol acetal derivative compound comprising the reaction of at least one aromatic benzaldehyde and at least one alditol in the presence of water, at least one mineral acid, and at least one surfactant. Furthermore, this invention encompasses a method of producing an alditol acetal derivative compound comprising the reaction of at least one-half mole of at least one aromatic benzaldehyde and at least one mole of an alditol in the presence of water, at least one mineral acid, and at most 0.01 mole (in relation to the amount of benzaldehyde present) of a surfactant. The actual reaction mixtures for these methods are also encompassed within this invention as well.
It has now been found that the addition of small molar amounts of long-chain surfactant to the reaction mixture permits a more effective yield of acetal alditol derivatives result through mineral acid catalysis of benzaldehyde and alditol components. Furthermore, such an inventive procedure permits tailoring of solubilities, and potential reduction of mineral acid amounts and/or concentrations to permit a more environmental, safe reaction as well.
Any alditol acetal derivative compound may be produced by the inventive method, including, as preferred but not as the limited type of alditol acetal compound, DBS compounds. Specific DBS derivatives produced by this inventive method include, as merely examples: 1,3:2,4-dibenzylidene sorbitol; 1,3:2,4-bis(p-methylbenzylidene)sorbitol; 1,3:2,4-bis(p-chlorobenzylidene)sorbitol; 1,3:2,4-bis(2,4-dimethyldibenzylidene)sorbitol; 1,3:2,4-bis(p-ethylbenzylidene)sorbitol, abbreviated as EDBS; 1,3:2,4-bis(3,4-dimethyldibenzylidene)sorbitol, abbreviated as 3,4-DMDBS; 1,3:2,4-bis(3,4-diethylbenzylidene)sorbitol; 1,3;2,4-bis(3-ethyl4-methylbenzylidene)sorbitol; 1,3:2,4-bis(4-chloro-3-methylbenzylidene)sorbitol, 1,3:2,4-bis(3-chloro-4-methylbenzylidene)sorbitol, 1,3:2,4-bis(3-bromo-4-isopropylbenzylidene)sorbitol, 1,3:2,4-bis(3-bromo-4-methylbenzylidene)sorbitol, and 1,3:2,4-bis(3-bromo-4-ethylbenzylidene)sorbitol. Other compounds include monoacetal derivatives, such as, without limitation 2,4-mono(3,4-dimethylbenzylidene)sorbitol, 2,4-mono(4-fluoro-3-methylbenzylidene)sorbitol, and the like (e.g., instead of two moles of aromatic aldehyde, only one is reacted with the alditol) and tri-acetals (e.g., three moles of aromatic aldedhyde to one of alditol). Furthermore, asymmetrical compounds may be produced, such as, without limitation: 1,3-O-(3,4-dichlorobenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3,4-difluorobenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3,4-dichlorobenzylidene):2,4-O-(3,4-dimethoxybenzylidene)sorbitol, 1,3-O-(3,4-dichlorobenzylidene):2,4-O-(5-indanylidene)sorbitol, 1,3-O-(4-nitrobenzylidene):2,4-O-(3,4dimethylbenzylidene)sorbitol, and 1,3-O-(4-nitrobenzylidene):2,4-O-(3,4-methylenedioxybenzylidene)sorbitol, 1,3-O-(4-fluoro-3-methylbenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3,4-dimethylbenzylidene):2,4-O-(4-fluoro-3-methylbenzylidene)sorbitol, 1,3-O-(4-fluoro-3-methylbenzylidene):2,4-O-(3-fluoro-4-methylbenzylidene)sorbitol, 1,3-O-(3-fluoro-4-methylbenzylidene):2,4-O-(4-fluoro-3-methylbenzylidene)sorbitol, 1,3-O-(4-fluoro-3-methylbenzylidene):2,4-O-(4-chlorobenzylidene)sorbitol, 1,3-O-(4-chlorobenzylidene):2,4-O-(4-fluoro-3-methylbenzylidene)sorbitol, 1,3-O-(4-chloro-3-methylbenzylidene):2,4-O-(3-chloro-4-methylbenzylidene)sorbitol, 1,3-O-(3-chloro-4-methylbenzylidene):2,4-O-(4-chloro-3-methylbenzylidene)sorbitol, 1,3-O-(4-fluoro-3-methylbenzylidene):2,4-O-(5xe2x80x2,6xe2x80x2,7xe2x80x2,8tetrahydro-2-napthylidene)sorbitol, 1,3-O-(5xe2x80x2,6xe2x80x2,7xe2x80x2,8xe2x80x2-tetrahydronapthylidene):2,4-O-fluoro-3-methylbenzylidene)sorbitol, 1,3-O-(4-Chloro-3-methylbenzylidene)-2,4-O-(5xe2x80x2,6xe2x80x2, 7xe2x80x2,8xe2x80x2-tetrahydro-2-napthylidene)sorbitol, 1,3-O-(5xe2x80x2,6xe2x80x2,7xe2x80x2,8xe2x80x2-tetrahydronapthylidene):2,4-O-(4-chloro-3-methylbenzylidene)sorbitol, 1,3-O-(3-bromo-4-ethylbenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3-bromo-4-isopropylbenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3-bromo-4-methylbenzylidene):2,4-O-(3,4-dimnethylbenzylidene)sorbitol, 1,3-O-(4-chlorobenzylidene):2,4-O-(3-bromo-4-isopropylbenzylidene)sorbitol, 1,3-O-(4-t-butylbenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3,4-dimethylbenzylidene):2,4-O-(t-butylbenzylidene)sorbitol, 1,3-O-(3,4-dimethoxybenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3,4-dimethylbenzylidene):2,4-O-(3,4-dimethoxybenzylidene)sorbitol, 1,3-O-(3,4-methylenedioxybenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3,4-dimethylbenzylidene):2,4-O-(3,4-methylenedioxybenzylidene)sorbitol, 1,3-O-(4-isopropylbenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol, 1,3-O-(3,4-dimethylbenzylidene):2,4-O-(4-isopropylbenzylidene)sorbitol, 1,3-O-(3,4-dimethylbeznylidene):2,4-O-(2-naphthylbenzylidene)sorbitol, and 1,3-O-(2-naphthylbenzylidene):2,4-O-(3,4-dimethylbenzylidene)sorbitol.
Such a diacetal compound, as well as any type of DBS system, may be produced through the condensation reaction between two moles of an aromatic aldehyde and one mole of a polyhydric alcohol. The aldehyde and polyhydric alcohol are generally provided in the reaction mixture in a ratio from 1:1 to 4:1, preferably 1.5:1 to 2.5:1, respectively. The aromatic aldehydes are single or fused double ring aldehydes having at least one unsaturated hydrocarbon ring, and include benzaldehyde, naphthaldehyde, 5-formylindan and 6-formyltetralin. The aromatic aldehydes may be unsubstituted or have from one to five substituent groups selected from C1-6 alkyl, C1-6 alkoxy, hydroxy, halogen, C1-6 alkylthio, C1-6 alkylsulfoxy, C3-5 alkylene forming a carbocyclic ring with adjacent carbon atoms on an unsaturated hydrocarbon ring, carboxyl, (C1-C20 alkyloxy)carbonyl, (C1-C20 alkyloxy)ethyloxycarbonyl, (C1-C12 alkyl)phenyl, halogenated phenyl, (C1-C12 alkoxy)phenyl, (C1-C12 alkyloxy)ethyloxyethyloxycarbonyl and (C1-C12 alkyloxy)ethyloxy-ethyloxyethyloxycarbonyl groups, methylenedioxy (e.g., piperonal), or any of the benzylidene groups may be polyphenyl (such as naphthyl). Preferably, the aromatic aldehyde is selected from unsubstituted benzaldehyde, benzaldehyde having from one to three substituent groups selected from C1-4 alkyl, halogen and C3-5 alkylene forming a carbocyclic ring with adjacent carbon atoms on an unsaturated hydrocarbon ring, including p-methyl, p-ethyl, 2,4-dimethyl, 3,4-dimethyl and 2,4,5-trimethyl benzaldehyde, 5-indan aldehyde and 5xe2x80x2, 6xe2x80x2, 7xe2x80x2, 8xe2x80x2-etrahydro-2-naphthaldehyde, or any of the corresponding benzaldehydes to the asymmetric or monoacetal compounds listed above. Of course, in order to produce mostly monoacetal compounds, a molar ratio of alditol to benzaldehyde of about 1:1 is necessary while triacetals require about a 1:3 molar ratio in general.
Mixtures of the aromatic aldehydes may be provided and will result in a distribution of diacetals having the same or different aromatic components, referred to as symmetric and asymmetric diacetals, respectively. The aromatic aldehydes typically react with the polyhydric alcohol to form acetals in the 1:3 and 2:4 positions. Also within the scope of the present invention are triacetals formed by the condensation of three moles of an aromatic aldehyde and one mole of a polyhydric alcohol having six or more hydroxyl groups. The triacetals are typically formed at the 1:3, 2:4 and 5:6 positions of the alcohol.
The polyhydric alcohols have five or more hydroxyl groups. The sugar alcohols represented by the formula HOCH2(CHOH)n CH2OH, where n=3-5, have been found to be especially useful. Preferably, the polyhydric alcohol is a pentahydric or hexahydric alcohol, most preferably xylitol or sorbitol. The polyhydric alcohol can be added to the reaction mixture as a solid, molten liquid, or as an aqueous solution.
The reaction medium for this inventive procedure is water, although small amounts of other solvents (such as alcohols, benzene, and the like) may be present as minor impurities. The water may also comprise other consituents such as salts (e.g., chlorides, sulfates, and the like), although it is preferred that the water be deionized prior to utilization within the method. The aqueous nature of this inventive process thus provides a cost-effective process (with such a plentiful, inexpensive, reusable, raw material) which is safe to handle and use, for clear reasons.
The mineral acid is selected from primarily hydroacids, such as, without limitation, hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, sulfurous acid, carbonic acid, phosphorous acid, and the like. Such a component is used as the actual catalyst to effectuate the acetalization of the alditol backbone. Although concentrated varieties of such acids are possible, it has also been found that not only is a safer reaction permitted through utilization of less concentrated compositions (for instance, and without limitation, instead of 12M HCl, concentrations of from 5 to 7, more preferably about 6 to 6.5M HCl), but a more effective reaction in terms of yield of acetal alditol product is potentially available as well. This phenomenon is more prevalent which symmetrical DBS compounds are formed, although asymmetrical DBS compounds may also benefit from such a concentration reduction.
As noted above, the catalysis of reactants within the inventive reaction mixture is highly dependent upon the ability of the catalyst to actually contact and thus effectuate catalysis between the components of the mixture itself. Solubility of components within the aqueous acid system is thus of utmost importance; more thorough mixing (and thus greater contact) between catalyst and components permits more effective and higher yields of acetal alditol product. The surfactant component of this inventive reaction is thus of utmost importance as well to effectuating the desired high yield, high purity results. The types of surfactants proper for such a reaction are virtually endless and may be tailored for certain situations, including, without limitation, the solubility of the benzaldehydes within the aqueous acid reaction mixture, environmental considerations, handling issues, cost, availability, compatibility with other components, and the like. Thus, the list of possible surfactants are those which are anionic, cationic, amphoteric, zwitterionic, and nonionic in nature. Compositions of more than one such surfactant may be utilized within the inventive process as well. For this invention, the broad term surfactant is intended to include any long carbon chain (e.g., 6 carbons or greater)-containing compounds with pendant groups such as, without limitation, hydroxyls, alkoxyls, carboxylates and acids, sulfonic acids and sulfonates, quaternary ammoniums, phosphoniums, phosphonic acids and phosphonates, and the like. As anionics, more specific types may be sulfonates, including long-chain substituted-arylsulfonic acids, and the like; cationics include quaternary ammonium salts, phosphonium salts, protonated long chain amines, and the like; nonionics include long-chain substituted phenols, alkoxylated alkanes and alkenes, long-chain alkylarnines, including octadecyl phenol, and the like. The amount of such surfactants added within the inventive reaction and inventive reaction mixture is in relation to the amount added of the benzaldehyde.
The molar ratio between benzaldehyde added and surfactant(s) is from about 1:0.1 to about 1:0.000001; preferably from about 1:0.05 to about 1:0.0001; more preferably from about 1:0.02 to about 1:0.0005; and most preferably between about 1:0.01 and 1:0.0005. In such a situation, the amount added of benzaldehyde is dictated by the type of acetal alditol product desired (mono-, di-, or tri-acetal) in relation to the molar amounts needed of the alditol component. The amount of aqueous acid to be added should be from about 1 to 5 times the amount of the total weight of benzaldehyde and alditol present, with concentrations anywhere between about 2M and 18M depending upon the acid used.
The reaction takes place at room temperature, enerally, although some heating may be followed. Some acids also react exothermically with water (such as sulfuric acid) to generate some internal heat within the system itself All of the components may be mixed together initially, or the surfactant and acid may be first mixed together (under heat, if desired), with subsequent addition of the reactants. The time for reaction may take anywhere from a few minutes (e.g., 10 minutes, as one non-limiting example) to a few days (e.g., 48 hours, as one non-limiting example) depending upon the batch size and the amount of acid catalyst present. Generally, a reaction time of from about 8 hours to about 48 hours, more preferably from about 8 hours to about 36 hours, is sufficient to produce the desired high yield acetal alditol derivatives. Upon production, a solid precipitate is generally formed and neutralized to a pH of from about 6 to about 9.5, with a pH of from about 7.5 to 9, more particularly from about 8.5 to 9, to permit safer handling. Any neutralizer for mineral acids may be utilized such as strong bases like sodium hydroxide, potassium hydroxide, and the like, for this purpose. The washed product can then be dried and collected as a crystalline structure for further utilization in a variety of procedures.